Sodium stannate catalyst for hydroxyalkylation of phenols or thiophenols

ABSTRACT

Hydroxyalkylphenyl ether or thioether compounds are prepared by reaction of cyclic organic carbonate compounds with phenols or thiophenols in the presence of Na 2  SnO 3  catalyst.

BACKGROUND OF THE INVENTION

The present invention relates to a process for the preparation ofhydroxyalkylphenyl ether or thioether compounds. More particularly, thepresent invention is concerned with an improved catalyst for use in thepreparation of such compounds by the reaction of cyclic organiccarbonate compounds with phenols and thiophenols.

Carlson disclosed in U.S. Pat. No. 2,448,767 a method ofhydroxyethylation wherein ethylene carbonate or ethylene sulfite wasreacted with certain organic compounds including phenols and alcohols.The reaction could be carried out in the presence or in the absence of asuitable solvent, and in the presence or in the absence of a suitablecatalyst. Catalysts that were disclosed included an acid (concentratedsulfuric acid or an alkyl ester of sulfuric acid), a base (alkalicarbonates), or the alkali salt of a phenol. The preferred catalyst wasan alkali carbonate or alkali salt of a phenol. U.S. Pat. No. 3,283,030disclosed use of potassium carbonate as a basic catalyst in the reactionof ethylene carbonate with certain substituted phenols.

Alkali metal hydrides disclosed by U.S. Pat. Nos. 2,987,555 and alkalimetal hydroxides disclosed by U.S. Pat. No. 2,967,892 have also beenfound to be effective catalysts for hydroxyalkylation reactions ofethylene carbonate with phenols and chloromethylethylene carbonate withphenols respectively.

One disadvantage associated with prior art processes using acidic orbasic catalysts has been the occurrence of secondary reactions betweenthe hydroxyalkylphenyl ether product and the carbonate reactant formingquantities of undesirable side-products. A further disadvantage of knownprior art processes is the inability to use certain modified phenolic orthiophenolic compounds that are unstable under acidic or basic reactionconditions.

SUMMARY OF THE INVENTION

This invention comprises an improved process for the hydroxyalkylationof phenols or thiophenols providing high yields with good selectivity.In particular the invention comprises the use of sodium stannate as areaction catalyst for the reaction of phenols or thiophenols and cyclicorganic carbonate compounds. The ability to operate at a neutral pHaccording to the invention allows the reaction to be run underrelatively mild conditions thereby allowing utilization of reactantshaving a greater variety of functionality than has been possible underprior known methods. It is also possible utilizing the invented processto attain reaction conditions conducive to exclusivemonohydroxyalkylation of the phenol or thiophenol reactant. Thehydroxyalkylphenyl ether or thioether products formed according to thisinvention are used as solvents and in certain coatings as well as inadditional industrial applications.

DETAILED DESCRIPTION OF THE INVENTION

This invention lies in the discovery that sodium stannate acts as aneffective catalyst in the reaction of cyclic organic carbonate compoundswith phenols or thiophenols.

The amount of catalyst required to effectively catalyze thehydroxyalkylation reaction according to the present invention may varycompared to total reactant weight from about 0.1 percent to about 10.0percent. It is preferred to employ the catalyst in amounts from about0.5 percent to about 2.0 percent by weight.

The catalyst of this invention may be used by itself or in combinationwith other known hydroxyalkylation catalysts. The catalyst may also beemployed in an unsupported state or supported by attachment to inertsupportive means such as particles of alumina, silica gel, diatomaceousearths, porous glasses, zeolites, and the like. By the term zeolites isincluded modern synthetic resin zeolites useful as ion-exchangers aswell as the well-known naturally occurring mineral formations that maybe used with or without modification as ion-exchangers. Attachment ofthe catalyst to such materials is known, one such method having beendisclosed by J. H. Clark in J.C.S. Chem. Comm., 789 (1978).

The phenol- or thiophenol-containing compounds that may behydroxyalkylated by organic carbonate compounds according to thisinvention are extremely varied. Carlson in U.S. Pat. No. 2,448,767discloses a wide variety of reactive hydrogen-containing aromaticcompounds including phenol, thiophenol, alkaline salts of phenol,β-naphthol, and 8-hydroxyquinoline that are capable of undergoinghydroxyalkylation with alkyl carbonate compounds. Additionally Carlsontaught that all such compounds tested responded to the hydroxyalkylationreaction and it was believed all such compounds would be responsive.

Davis in U.S. Pat. No. 2,987,555 discloses an additional number ofphenols that may be hydroxyalkylated by reaction with alkylenecarbonates including: p,p'-biphenol, p,p'-sec-butylidene diphenol,4,4'-isopropylidenebis(o-cresol),4,4'-isopropylidenebis(2-phenylphenol), o-chlorophenol, o-cresol,p-propylphenol, p-bis(o-cresol) and the like.

I have found that nearly any phenol- or thio- phenol-containing reactantis suitable for use according to this invention. Included are: phenol,thiophenol, and phenol or thiophenol compounds substituted with one ormore hydroxy, mercapto, alkyl, aryl, alkaryl, aralkyl, halo or sulfonylsubstituents or mixtures thereof.

However, Tsuruya disclosed in J. Polymer Sci., Part B, 7, 709 (1969)that 2,4,6-tribromophenol, preferably forms polymers throughdebromination when reacted with organic carbonate compounds. Thiscompound therefore is not considered to be suitable for use according tothe present invention.

The cyclic organic carbonates used in the hydroxylation reactionsaccording to this invention may likewise be varied. In addition toethylene carbonate, Davis in U.S. Pat. No. 2,987,555 disclosed that anycyclic alkylene carbonate having the appropriate carbonate moietyattached at adjacent positions was capable of undergoinghydroxyalkylation with phenolic compounds. Specifically mentionedcarbonate compounds were propylene carbonate, 1,2- or 2,3-butylenecarbonate and phenylethylene carbonate. For said disclosure I doincorporate this teaching by reference.

In addition, ethers of alkylene carbonates of the formula ##STR1##wherein R is C₁₋₂₀ alkoxy, alkoxyalkylene or (poly)alkoxyalkylene mayalso be used.

As previously mentioned, use of the instant catalyst at a neutral pH inthe practice of this invention instead of acidic or basic catalystsadvantageously permits the use of reactants containing greaterfunctionality. The catalyst and milder reaction conditions additionallyallow greater selectivity in product formation including the exclusiveformation of the monohydroxyalkylated product without concomitantformation of secondary reaction products.

The reaction may take place in the presence or absence of an inertsolvent. In the preferred embodiment the cyclic carbonate reactant is asuitable solvent.

The reactants may be combined in nearly any molar ratio since someproduct is produced under nearly all conditions. It is preferredhowever, to combine the reactants in a stoichiometric ratio therebyeliminating the need to remove excess reactants from the finishedproduct in a subsequent purification step.

The reaction may be carried out in any vessel suitably designed tocontain the reactants and products and be unreactive under theconditions of the invention. Representative of suitable reaction vesselsare those made of glass, stainless steel or other unreactive material.

The reaction may be run in the practice of this invention at anysuitable temperature from about 100° C. to about 210° C. Faster reactionrates are observed at higher temperatures but decomposition of reactantsand products is likely to occur at the higher temperatures. The optimumtemperature for particular reactants allowing fast reaction rates, butminimizing decomposition side-products may be easily determinedaccording to ordinary techniques of experimentation. The preferredoperating temperature for most phenolic and carbonate reactants is fromabout 150° C. to about 170° C. Heating the reaction vessel to theoperating temperature may conveniently be occasioned by any usual meanssuch as a heat lamp, heating mantle, oil bath, etc.

The time for the reaction to proceed to substantial completion will varydepending on various factors such as the particular phenol- orthiophenol-containing reactant, cyclic organic carbonate reactant, andtemperature selected. Generally about two hours to about five hours issufficient. The evolution of carbon dioxide is a convenient indicator ofthe progress of the reaction.

The reaction may be run either accompanied by mechanical or magneticstirring or without stirring. To avoid liquid entrapment during theevolution of carbon dioxide it is also advantageous to employ acondenser according to well-known techniques in the art.

The product, a corresponding hydroxyalkyl ether or thioether derivativemay be easily recovered from the reaction mixture, for example, bydistillation if a liquid, or by recrystallization if a solid.

While the invention has been described as useful in a batch processreaction, it may be utilized equally advantageously in a continuousreaction process.

SPECIFIC EMBODIMENTS OF THE INVENTION

Having described the invention the following examples are given merelyas illustrative of the present invention and are not to be considered aslimiting.

EXAMPLE 1

Ethylene carbonate (45 g, 0.51 mole), phenol (47.1 g, 0.5 mole) andsodium stannate (0.5 g, reagent grade) were placed in a 250 ml glassround-bottomed flask equipped with a condenser and gas bubbler.Agitation was provided with a magnetic stirrer. The mixture was heatedto 160° C.±2° C. in an oil bath. After the time indicated in Table I,the reaction vessel was removed from the oil bath and purified bydistillation. The product was identified as 2-phenoxyethanol. Resultsare provided in Table I.

EXAMPLE 2

The conditions of Example 1 were repeated utilizing as catalysts otherinorganic and organic salts. The results indicated a relative lack ofcatalytic activity in the compounds. The results are contained in TableI for comparison purposes.

                  TABLE I                                                         ______________________________________                                                      Reaction                                                                      Time         Percent                                            Compound      (hrs.)       Completion                                         ______________________________________                                        Na.sub.2 SnO.sub.3                                                                          4.0          95                                                 FeSO.sub.4    6.0          41                                                 NH.sub.4 [OC(O)CH.sub.3 ]                                                                   6.0          43                                                 Zn[OC(O)CH.sub.3 ].sub.2                                                                    6.0          39                                                 Cu[OC(O)CH.sub.3 ].sub.2                                                                    5.0          10                                                 MgO           6.0          14                                                 (C.sub.4 H.sub.9).sub.4 NHSO.sub.4                                                          5.5          12                                                 K.sub.2 HPO.sub.4                                                                            4.25        12                                                 ______________________________________                                    

EXAMPLE 3

The reaction conditions of Example 1 were repeated using as a catalystabout 5 g of an aqueous 50 percent solution of NaOH. After reaction for3 hours the product was analyzed. Ethylene carbonate conversion wasabout 90 percent but the product contained higher oligomeric reactionproducts. No higher reaction products were observed utilizing Na₂ SnO₃.

What is claimed is:
 1. In the method of hydroxyalkylation whereinphenol- or thiophenol-containing compounds are reacted with cyclicorganic carbonate compounds, selected from the group consisting ofethylene carbonate, propylene carbonate, 1,2- or 2,3-butylene carbonate,phenylethylene carbonate, and ethers of alkylene carbonates of theformula ##STR2## wherein R is C₁₋₂₀ alkoxy, alkoxyalkylene or(poly)alkoxyalkylene, in the presence of a catalyst followed by recoveryof the hydroxyalkylaryl ether formed, the improvement wherein thecatalyst is sodium stannate.
 2. The process of claim 1 wherein thereaction is carried out at approximately neutral pH.
 3. The process ofclaim 1 wherein the phenol- or thiophenol-containing compound andorganic carbonate compound are combined in substantially stoichiometricquantity.
 4. The process of claim 1 wherein the carbonate compound isethylene carbonate.
 5. The process of claim 1 wherein the reaction iscarried out at a temperature from about 100° C. to about 210° C.
 6. Theprocess of claim 1 wherein the quantity of catalyst present based ontotal reactant weight is from about 0.1 percent to about 10 percent. 7.The process of claim 1 wherein the phenol- or thiophenol-containingcompound is phenol.